Watchmen (R) ***

Zack Snyder’s ambitious, long-awaited adaptation of the groundbreaking graphic novel Watchmen accomplishes something almost miraculous. It excises much of the striking peripheral material that made the genre-smashing Alan Moore/ Dave Gibbons comic — about superheroes who are anything but noble — so complex, deeply layered and compelling while still slavishly following its plot, practically panel by panel.

Such allegiance to printed material doesn’t always translate to film, and fans will doubtless mourn some of the losses (though few can argue convincingly that the comic’s climactic Giant Squid sequence would have worked on screen). Grumpy Moore will probably grumble loudest of all. But with its basic themes, structure and apocalyptic vibe intact, Watchmen turns out to be quite filmable after all, and its stylish highlights trump any quibbles.

Snyder (300, Dawn of the Dead) uses a spectacular series of opening credits to set the stage. We witness the evolution of the superheroes, from the Minutemen circa World War II to the more modern Watchmen, to the tune of Bob Dylan’s The Times They Are A-Changin’. Before you grimace and shout ”Cliché!” know that the song acts as a fitting bookend to My Chemical Romance’s version of Dylan’s even more appropriate Desolation Row over the end credits.

The Watchmen’s best days are behind them in this alternate universe, though, since Richard Nixon — still president in 1985 when the story is set — won the Vietnam War with the help of big, blue and frequently nude superhero Dr. Manhattan (Billy Crudup) and his grinning, gun-toting, amoral sidekick The Comedian (Jeffrey Dean Morgan). But despite the rising threat of nuclear holocaust, Congress (the bastards) has outlawed superheroes, so these days former masks tend to keep a low profile. One exception is Ozymandias (Matthew Goode), a flashy-dressing entrepreneur who seems bent on cashing in on every possible version of himself as action-hero figure.

But then The Comedian is murdered, and the sociopathic Rorschach (Jackie Earle Haley) steps up to investigate whether some villain is knocking off superheroes with a big End Times endgame in mind. Along the way, he unites the self-doubting Nite Owl (Patrick Wilson) and the eager Silk Spectre (Malin Akerman), whose romance with Dr. Manhattan — whose powers are the result of an unfortunate mistake back at the ol’ physics lab — has started to sour as the blue man grows ever more detached from humanity.

Nihilism and self-interest aren’t qualities we expect in our superheroes, but those anti-archetypal qualities make these costumed freaks so intriguing. The Comedian indulges in attempted rape and point-blank murder. Nite Owl’s costume resembles Batman’s, but Bruce Wayne never had Nite Owl’s issues in the sack. And the unbending Rorschach and his affinity for torture make 24‘s Jack Bauer seem like the president of Amnesty International. Snyder’s refusal to indulge in A-list casting works wonderfully with the lesser-known Morgan, Wilson and Haley, all of whom are terrific (and Haley does most of his acting behind a shifting ink-blot mask). Even Crudup, who mostly uses his voice, is effective, his gentle tones an arresting contrast to Dr. Manhattan’s startling appearance.

Watchmen is a spectacularly violent movie; Rorschach’s dispatch of a child killer, for example, is far more gruesome in the film than in the comic. Axes split heads; saws rend limbs; tides of blood flow. Snyder positively revels in the slow-mo gore, but his camerawork is also effective in the film’s dark, quiet moments, such as when he captures the rain dripping slowly from Nite Owl’s glasses. And yes, the Mars sets are never quite convincing, and Akerman’s Silk Spectre lacks the complexity of her male colleagues (isn’t that always the way?). Dr. Manhattan’s discourses on humanity are occasionally a drag on the action, though the film never feels bloated even at its considerable length. Still, though Snyder could hardly follow Rorschach’s motto — ”Never compromise” — his faithful vision of this classic comic all worked out in the end.

Cast: Malin Akerman, Billy Crudup, Matthew Goode, Jackie Earle Haley, Jeffrey Dean Morgan, Patrick Wilson, Carla Gugino.

Director: Zack Snyder.

Screenwriters: David Hayter, Alex Tse. Based on the comics by Alan Moore and Dave Gibbons.

Producers: Lawrence Gordon, Lloyd Levin, Deborah Snyder.

A Warner Bros. release. Running time: 163 minutes. Strong graphic violence, sexuality, nudity, language. Playing at area theaters.